Displayed tubes such as neon signs are usually mounted in a display or sign housing supported on the exterior wall of a building and electrical connections are made through a conduit to a high tension wire extending through the conduit from the housing through the wall to the interior side of the wall to a power source. Electrodes are mounted on the opposite ends of a gas filled tube or neon sign and are adapted for connection to the ends of the high tension wires.
Since relatively high voltages in the vicinity of 7500 volts are utilized to excite the neon tubes an electrode receptacle or socket has been developed so as to avoid the manual engagement of the electrodes of the neon signs to the high tension wires.
Such electrode sockets usually comprise a cylindrical receptacle or socket which is adapted to be mounted within a cylindrical metal housing and which is adapted for mounting through the building wall on which the sign is mounted. One end of the receptacle which is mounted within the building wall includes a compression spring attached to an electrical contact which is connected to the high tension wires, while the other end of the electrode receptacle includes an opening to telescopingly receive the electrodes at the end of the neon tube for contact with the compression spring, electrical contacts and high tension wire at the other end of the electrode socket. Once the neon tube is inserted into the receptacle the compression spring is compressed so as to effect a good electrical contact. In this way, the electrical connection to the tube is made within the interior of the electrode socket away from the manual engagement and the connection is made automatically upon insertion of the neon tube into the electrode receptacle.
The electrode receptacles have heretofore been made from materials having high dielectric characteristics as insulators such as glass or porcelain.
For example, U.S. Pat. No. 1,872,593 discloses an electrode housing made of porcelain. U.S. Pat. No. 1,890,680 teaches a socket which consists of tubular glass or porcelain. Moreover U.S. Pat. No. 2,046,960 teaches the use of an insulator made of Pyrex type or Boro-Silicate glass composition. Finally, U.S. Pat. Nos. 2,486,497 and 2,561,954 show the use of a receptacle or socket made of glass.
The utilization of such fragile material as glass or porcelain in the manufacture of electrode receptacles cause problems in the installation of same as glass or porcelain cracks if mishandled or over tightened. Furthermore, glass and porcelain crack due to changing weather conditions, temperature changes caused by seasonal changes as well as sudden surges of high voltages which vaporize water that tends to collect in the electrical receptacles.
When the glass or porcelain receptacles present cracks, the high electrical voltages leak out or "arc" outwardly through the crack thereby creating a potentially hazardous.
Furthermore, when a building which contains neon tubes is under fire, the severe temperature of the fire as well as the structural damage caused thereby frequently causes the glass or porcelain receptacles to break thereby exposing the high voltages and further creating a dangerous condition.
Also the compression springs used heretofore have a tendency to loose their compressibility or resiliency as a result of the turning on and off of neon tubes over an extended period of time. When neon tubes are turned on or excited by the application of the relatively high voltages the compression spring has a tendency to heat up and expand; and the compression spring has a tendency to cool off or contract when the neon tubes are turned off. Over time this repetitive expansion and contraction of the compression spring causes the spring to loose its resiliency or compressibility to such an extent that the spring may no longer contact the end of the neon tube since the neon tube is anchored to the building wall. When this condition is reached the high electrical voltages arc between the space between the compression spring and end of the neon tube, causing the neon tube to flicker on and off and the neon tube eventually fails. Furthermore the resulting arcing becomes a potential hazard.